Effects of Ca²⁺ and La³⁺ in Y_1-xCa_xBa_2-xLa_xCu₃O_y study - An X-ray absorption spectroscopy

A series of samples, Y_1-xCa_xBa_2-xLa_xCu₃O_y (x = 0 ∼ 0.6), were prepared and studied by X-ray absorption near-edge spectroscopy (XANES). The oxygen content y in these samples remained about the same for all x. Both the O-1s and Cu-2p_3/2 XANES results indicate that the total number of holes remained essentially unchanged. The O-1s XANES gives no sign showing that there are La ions on the Y sites. Our data indicated that the Ca²⁺ and La³⁺ doping changed not only the lattice symmetry but also the electronic structure at the Fermi energy in the valence band. The results derived from the O-1s XANES showed that the holes on the CuO₂ planes decreased, while the holes on the O(1) and O(5) sites en the basal plane increased, as the doping concentration x increased.